This invention relates to watch cases, and more particularly, to a fixing structure for fixedly retaining a watchglass, a bezel, or a back cover within such a watch case.
A conventional watch case has a fixing structure for fixedly retaining a watchglass, a bezel or a back cover in the bezel or a case band, respectively. The fixing structure usually employs a synthetic resin gasket, which is compressed between the outer circumference of, for example, a watchglass and the inner circumference of, for example, a case band. In this case, the watchglass and the gasket are fixedly retained against the axial movement due to the frictional force existing therebetween, and the case band and the gasket are fixed against the axial movement due to the frictional force existing therebetween. Since the fixing force between the gasket and the case band is greater than that between the watchglass and the gasket, the gasket must be subjected to a large compression force in the direction of its diameter in order to provide a sufficient fixing force and water-tight seal over a long period of time. However, when a large amount of compression is applied, the gasket protrudes excessively in the axial direction at the time that it is press fitted about the outer circumference of the watchglass. The same problems arise in the fixing structure between the watchglass and the bezel, between the bezel and the case band or between the back cover and the case band. It is therefore not possible to obtain reliable fixing force and water-proofness. In order to solve these problems, it has been proposed to increase the height of the watchglass, bezel, case band or the back cover so as to increase the fixing force between the adjacent members. As a result, it is extremely difficult to provide a watch case having a reduced thickness.
It is, therefore, an object of the present invention to provide a fixing structure that makes it possible to minimize watch case thickness.
It is another object of the present invention to provide a watch case for water-proofing and fixedly securing a watchglass, a bezel or a back cover.